DESCRIPTION: Development of non-metallic (e.g., amalgam-substitute) restorative materials is a high research priority due to environmental concerns associated with metals waste and disposal. Ceramics are an ideal candidate for replacing metal-based restorative materials. Ceramics provide excellent chemical durability; wear resistance, biocompatibility, environmental friendliness, and esthetics. Nevertheless, widespread all-ceramic restoration use has been hindered by concerns related to marginal fracture resistance and clinical longevity. Previous studies found that clinical fracture of all-ceramic restorations initiated along internal surfaces (e.g., bonded surfaces) almost exclusively. It is therefore critical to overcome fracture problems if these materials are to gain widespread acceptance. The overall goal of this continued research is to develop tougher, more fatigue-resistant all-ceramic dental restorations by minimizing or eliminating catastrophic effects of surface flaws through the implementation of RF-plasma sputter deposited thin-film ceramic surface coatings. Research conducted to date within the initial funded NIH grant has focused on microstructural control of deposited films and assessing their affect on the mechanical behavior of modified ceramic substrates. ZrO2 has been identified as the most appropriate thin film coating material. In addition, it has been found that ZrO2 thin-films produce no deleterious effect on bonding to a modified dental ceramic surface, or on the esthetic appearance of a translucent ceramic. The Specific Aims of this continued research are to: (1) test the hypothesis that the residual stress state and distribution within sputter deposited ZrO2 thin-films can be reproducibly controlled through manipulation of deposition parameters to produce constructs with predictable fracture resistance, (2) test the hypothesis that deposition of multi-layered thin-films with alternating high and low modulus layers can be used to produce substrate/thin-film laminate constructs with significantly greater facture toughness than is achieved with single-layer thin films, and (3) test the hypothesis that incorporation of sputter deposited ZrO2 thin-films will significantly enhance the fatigue resistance of specimens fabricated from traditional commercially available Dental ceramic materials. This technology needs further study to establish a more detailed understanding of the relationships between deposition parameters, thin-film microstructures, and short and long-term mechanical behavior of modified ceramics if a clinically efficacious process is to be developed.